The Farmers Union of Wales (FUW) said CAP’s dismantling would precede the growth of large, ranch farming that was unsuited to the environmentally-sensitive hills of Wales.

Senior policy officer Rhian Nowell-Phillips said: “Whilst we welcome the recognition of the importance of food production, we are fundamentally opposed to the abandonment of the CAP as the loss of support payments would be particularly devastating in Wales

“The whole idea of the CAP was to prevent the re-nationalisation of agriculture and we suspect that, if this happened, the British government would be far less supportive of its farmers than, say, France.”

Launched at this week’s Oxford Farming Conference, Food 2030 is the UK’s first major food chain strategy in 60 years.

Mr Benn said the way food is produced, consumed and disposed of will all have to change over the next two decades in response to climate change, population increases and competition for natural resources, especially oil and water.

He said: “We need to produce more food. We need to do it sustainably. And we need to make sure that what we eat safeguards our health.”

Food 2030 does not go into detailed policy proposals but sets out six key challenges for the food system. Few of these attract firm investment commitments, other than existing rural development funding.

It calls for farming sectors that are “without reliance on subsidy or protection”, and demands that agriculture increases production while lessening its impact on the environment.

For this to happen farming leaders say there must be more food research.

Yesterday the government launched a new science strategy. As well as a new food security research programme, £90m will be spent over five years to fund a new Sustainable Agriculture and Food Innovation Platform.

Key future technologies are expected to include GM, nanotechnology, crop productivity, genomics – particularly in livestock – and new water and soil technologies.

In Wales, the Institute of Biological, Environmental and Rural Sciences (Ibers), Aberystwyth, is investing £55m in new facilities in a bid to become one of the world’s top three land-based university departments.

“The challenges facing us all require pioneering new methods of farming,” said Huw McConochie, of Ibers.

But critics say Food 2030 isn’t up to the job. Speaking at the Oxford Farming Conference, John Parker, of The Economist magazine, said farmers need to double livestock production by 2050, and boost cereal production by 40% to avoid a future food crisis.

He said a technological breakthrough was needed of the scale of the ‘Green Revolution’ in the 1960s.

The NFU said Food 2030 was a useful blueprint but the government now needed to implement policies that underpinned its aspirations.

And while the Soil Association hoped the strategy would herald a return to less intensive farming systems, the Food Ethics Council said a leaner agricultural sector would damage family farming and bring hunger to the poorest people.

The industry welcomed Tory pledges to introduce a supermarket ombudsman as a step in the right direction.